1. Technical Field
The present invention relates generally to dynamically adjustable hybrid two-way data networks, and more particularly pertains to dynamically adjustable hybrid two-way data networks.
The majority of residential customers can use 33.6 Kbps (and possibly 56 Kbps) dial-up telephone connections to on-line services. The popularity of the web has increased substantially the number of people served by on-line service providers, but the slow speeds associated with surfing the web and downloading information from it via telephone modems quite often make this experience a painful one. True interactive broadband services is out of the reach of the majority of small office/home office (SOHO) and general residential customers.
The development of cable modem technologies for hybrid fiber/coaxial (HFC) CaTV networks promises the advent of multi-Mbps interactive broadband services to residential customers. The exploitation of the large excess bandwidth on an HFC CaTV plant would permit customers to cruise the web and enjoy other interactive services at speeds that are 100-fold or more than what is possible today.
While two-way communications over the telephone network has been maturing for more than a century now, two-way communication networks based upon the CaTV infrastructure is still in its infancy. Considerable effort is required for developing not only the data transport mechanisms needed for transporting data back and forth over the shared-medium CaTV plant, but also the network management protocols which will guarantee high-availability of the CaTV plant for practically uninterrupted digital services to customers.
Due to the tree-and-branch topology of a CaTV network, there is no possibility of "re-routing" transmissions around a cut in the cable network. Hence, a single cut of the cable could throw a whole community of customers out of service for a long period of time. Even worse, the frequency spectrum from 5 to 42 MHZ which will be used for upstream transmissions, i.e., from the cable modem to the CaTV headend (H/E), is prone to ingress noise interference from unterminated CaTV outlets, ham radio, short-wave radio, impulse noise, etc. All of this noise is further amplified as it travels to the H/E due to the noise funneling effect.
2. Prior Art
Currently available static CaTV/PSTN (Public Switched Telephone Network) systems use PSTN for upstream transmissions, and the CaTV plant for downstream transmissions. The use of static hybrid networks with CaTV on the downstream side and PSTN on the upstream side has been introduced during the last few years to provide a fast entry to the interactive CaTV arena, with "off-the-shelf" solutions which do not require a fully two-way operational CaTV system.
U.S. Pat. No. 5,586,121 discloses static hybrid networks where the use of the same or a different communications channel is suggested for the forward and return channels. Also, U.S. Pat. No. 5,534,913 discloses an apparatus and method for integrating downstream data transfer over a cable television channel with upstream data carrier by other media. U.S. Pat. No. 5,488,412 teaches a customer premises equipment which receives high-speed downstream data over a cable television system and transmits lower speed upstream signaling on a separate channel.